The invention relates to a switching element for a valve drive of an internal combustion engine, preferably for deactivating a valve. Said element comprises an outer section, in addition to an inner element that can be axially displaced in the bore of the outer section. According to the invention, the outer section and the inner element are displaced away from one another by the action of lost-motion spring elements and can be coupled together in an axially-distant relative position, whereby at least one piston, which is situated in a bore that runs transversally through the inner element, is applied as the coupling element. An annular groove, into which the piston can be partially displaced to adopt its coupling position, is provided in the bore of the outer section. Some sections of the underside of the piston have a flat transversal surface, which leads from the outer radial end face of the piston and acts as a contact zone for an opposing annular surface of the annular groove and the piston is held in the inner element by means of a rotational lock. Stop elements are allocated to an inner radial end face of the piston for the uncoupling position of the latter.
Such a switching element, here embodied as a roller tappet for a push rod drive, is known from U.S. Pat. No. 6,321,704, FIG. 6, which is considered to be a category-defining invention. An annular groove, in which a securing ring runs, is arranged in the outer casing of the inner element of the switching element. In the region of a radial bore for the shown two pistons intersecting the outer casing of the inner element, as coupling elements the securing ring engages under a flattened underside of the piston. This securing ring is used as a rotational lock for the piston in its radial bore in the inner element, whereby an allocation of its flat underside to the annular groove in the outer section is guaranteed in the coupling case.
A recess, which carries a ring-shaped element for defining a stop for the inner radial piston, is also formed in the middle in the radial bore.
Several disadvantages are inherent in the previously mentioned configuration. For example, according to processing, significant residual burrs remain in the region of an outlet of the annular groove on the outer casing of the inner element in the section of the radial bore. These must be removed, which is expensive. Simultaneously, it is clear to someone skilled in the art that the total production of two annular grooves for the rotational lock as well as the inner radial stop requires additional expense.
In addition, the previously mentioned document presents no measures like preventing processing-specific tolerance problems and symmetry errors with simple means.